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Vulnerability of ordinary moment resistant concrete frames

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Earthquake eng.neering and eng.neering Vibration 2011年第4期10卷 519-533页

作者： Mohammad Barkhordary Saeed Tariverdilo department of Civil eng. Faculty of Eng.Urmia University

The effects of structural modeling （bar slip in lap splice）, ground motion selection process （epsilon effect） and size of a structure （number of bays and stories） on the fragility of reinforced concrete ordinary moment resisting frames are investigated. An analytical model is developed to account for bar slip in lap splice, which exhibits good correlation with existing experimental data. Then, incremental dynamic analysis is used to derive the fragility curves for four model structures. The model structures simulate frames with a different number of bays and stories. Finally, the fragility curves are corrected for the epsilon effect. The results show that slip in the lap splice can significantly increase the failure probability, especially for the collapse prevention limit state. At the same time, it is found that spectral shape has a significant impact on the fragility curves. It is also found that accounting for or ignoring bar slip or epsilon effects increases the probability of failure for larger structures. This indicates an unconservative bias in the safety of larger structures.

关键词： lap-splice slip incremental dynamic analysis fragility curve epsilon effect

Predication of Plastic Flow Characteristics in Ferrite/Pearlite Steel Using a Fern Unit Cell Method

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上海交通大学学报 2004年第Z2期38卷 61-66页

作者： Hong Li Jingtao Han Jing Liu Lv Zhang School of material Sci. & eng. Univ. Of Sci. &Tech. Beijing Beijing100083 China School of Material Sci. & Eng. Univ. Of Sci. &Tech. Beijing Beijing100083 China School of Material Sci. & Eng. Univ. Of Sci. &Tech. Beijing Beijing100083 China School of Material Sci. & Eng. Univ. Of Sci. &Tech. Beijing Beijing100083 China

The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculated based on unit cell model. The effects of volume fraction, distribution and the aspect ratio of pearlite on tensile properties have been investigated.

关键词： ferrite/pearlite steel unit cell flow curve finite element method simulation

Microstructure Study on Semi-solid 60Si2Mn during Compressing

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Journal of University of Science and Technology Beijing 2001年第2期8卷 115-118页

作者： Yonglin Kang, Xiongfei Yang, Renbo Song, Weimin Mao, Maosheng.Yang (material Science & eng.neering School, University of Science and Technology Beijing, Beijing 100083, China) material Sci. and eng. School University of Science and Technology Beijing 100083 China

The microstructure behavior and deformation mechanism of semi-solid 60Si2Mn fabricated by electromagnetic stirring under different deformation conditions during thixoforming are studied by means of Gleeble-1500 thermal-strain-stress simulator. The micro- structure of deformed 60Si2Mn and that of the non-deformed are compared. The results show that the grain size within deformation zone decreases as the amount of deformation increases or deformation temperature decreases, but deformation fate has small effect on grain size when the rate is very low. Besides, there is a critical amount of deformation to reduce grain size. These results offer theoretical and experimental basis for further producing semi-solid material with high melting temperature and direct forming of semi-solid slurry.

关键词： semi-solid microstructure grain size segregation, reduction

Effects of Nickel Distribution on the Streng.hening and Toughening of Alumina Ceramics

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Journal of materials Science & Technology 2008年第5期24卷 723-728页

作者： Mohamed.M.El-Sayed Seleman department of materials and Metallurgical eng. Faculty of Petroleum and Mining Eng.Post Code 43721SuezEgypt

Three types of composite materials were designed and fabricated by hot pressing powder blends of alumina with 20 vol. pct nickel particles. The composites differ in the shape, size and distribution of the nickel particles. Composite microstructures are described and measurements of density, hardness, flexure streng.h, and fracture toughness are reported. The results showed that the fracture streng.h of the composite with dispersed nickel particles is higher than the other two composites （network microstructure and mixed microstructure） and the alumina matrix. For all the composites studied, tougher materials than the monolithic alumina were produced. The fracture toughness of the composite with a network microstructure is much higher than that of the other composites. The toughening mechanisms were described based on the observation of the fracture surfaces and the crack-particle interactions. Moreover, the parameters for microstructural tailoring of these materials have been deduced. The toughening of the produced composites was explained in light of the interracial bond streng.h.

关键词： Alumina-nickel composites Nickel morphology Interfacial bonding Fracturetoughness Flexure streng.h

Syntheses and Drug Delivery Property of Biodegradable Polyether-Anhydrides

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Journal of Wuhan University of Technology(materials Science) 2001年第3期16卷 49-51页

作者：王钧 School of material Sci. and eng. Wuhan University of Technology Wuhan 430070 China

Both polyanhydrides and polyethers are new types of biodegradble polymers, They are of particular interest as materials for controlled drug release system duo to their excellent surface erosion properties of polyanhydrides and excellent biocompatibility of polyethers. They hate been widly used in biomaterials. A series of polyether anhydrides elastomer were firstly synthesed through introducing PEG into the polyanhydrides chains. Their degradation and drug release property were also studied. These materials may be used in applications where materials are needed with properties more close to those of natural skin.

关键词： biodegradable polymer drug release polyether-anhydride ciprofloxacin

XPS Studies of Magnetic Multilayers

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Journal of University of Science and Technology Beijing 2001年第3期8卷 210-213页

作者： Guanghua Yu, Hongchen Zhao, Jiao Teng. Chunlin Chai, Feng.u Zhu, Yang Xia, Shumin Chai material Science and eng.neering School, University of Science and Technology Beijing, Beijing 100083, China Microelectronics Center, Chinese Academy of Science, Beijin material Science and eng. School Univ. of Sci. and Technol. Beijing Beijing 100083 China

NiOx/Ni81Fe19 and Co/AlOx/Co magnetic multilayers were fabricated by reactive RF/DC magnetron sputtering on clean glass substrates and oxidized Si (100) substrates, respectively. The exchange biasing field (H-ex) between NiO4 and Ni81Fe19 as a function of NiOx oxidation states was studied by X-ray photoelectron spectroscopy (XPS). The oxidation states and the oxide thickness of Al layers in magnetic multilayer films consisting of Co/AlOx/Co were also analyzed. It is found that the H-sr of NiOx/Ni81Fe19 films only depends on Ni2+ but not on Ni3+ or Ni. The bottom Co can be completely covered by depositing an A I layer thicker than 2.0 nm. The oxide layer was Al2O3, and its thickness was 1.15 mn.

关键词： NiOx exchange biasing field H-ex AlOx X-ray photoelectron spectroscopy (XPS)

Study on Rare Earth-Containing Phases in TiAl Based Alloys Prepared by Non-Equilibrium Solidification Processing

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Journal of Rare Earths 2001年第2期19卷 103-106页

作者：马学沈军贾均 Sch. of material Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

Microstructure evolution of rare earth rich phase of rapidly-solidified (RS) TiAl based alloys was investigated. The two rapid-solidification techniques employed are melt-spinning technique (MS) and Hammer-and-Anvil technique (HB). MS ribbons and HA foils were obtained in the experiment. The results demonstrate that with the increasing of cooling rates of TiAl based alloys great changes are taken place in the microstructures of rare earth rich phase, from scattering mainly on grain boundaries of as-cast ingot to distributing homogeneously as very fine fibers or powders (nanometer grade) on the matrix. The fine paralleling second phase fibers in the HA foils are considered to be connected with gamma/alpha (2) lamellar colonies. Selected area electronic diffraction (SAED) patterns of the rare earth rich phase is in accordance with that of intermetallic AlCe.

关键词： rare earths rapid solidification rare earth rich phase TiAl based alloy microstructure

A Special TMCP Used to Develop a 800MPa Grade HSLA Steel

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Journal of University of Science and Technology Beijing 2001年第3期8卷 224-228页

作者： Cheng.ia Shang,Xuemin Wang, Xinlai He, Shanwu Yang, Yi Yuan material Science and eng.neering School, University of Science and Technology Beijing, Beijing, 100083, China material Science and eng. School Univ. of Sci. and Technol. Beijing Beijing 100083 China

The effect of relaxation after finished rolling on structures and properties of four microalloyed steel with different content of Nb and Ti was investigated. By alloy designing and control rolling + relaxation-precipitation-control phase trail storm ati on (RPC) process, a new 800 MPa grade HSLA plate steel could be obtained, the microstructure is composite ultra-fine lath bainite/martensite. The tempering process and mechanical properties of this kind of HSLA steel were investigated. The yield streng.h can achieve 800 MPa, and the ductility and impact toughness is satisfied.

关键词： HSLA steel microstructure and mechanical properties TMCP (thermomechanical control process) RPC

Relaxation of Deformed Austenite and Refinement of Bainite in a Nb-Containing Microalloyed Steel

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Journal of University of Science and Technology Beijing 2001年第3期8卷 214-217页

作者： Shanwu Yang, Xuemin Wang, Cheng.ia Shang, Xinlai He, Yi Yuan material Science and eng.neering School, University of Science and Technology Beijing, Beijing 100083, China material Science and eng. School Univ. of Sci. and Technol. Beijing Beijing 100083 China

By means of stress relaxation and strain-induced precipitation in deformed austenite, bainite with micron sheaves size was obtained in Nb-containing steel. Microstructures of deformed samples isothermally relaxed for various time followed by cooling in water were examined. Stress relaxation test and transmission electron microscopy (TEM) were employed to detect precipitation of microalloy elements, such as Nb, Ti, during isothermal holding after deformation. All the samples were constituted by lath-like bainite along with acicular ferrite, but the size of bainitic sheaves and the amount of acicular ferrite were changed with relaxation time. To achieve optimum refinement, relaxation should be confined in the stage when the precipitates have sufficiently grown and started to coarsen. The sample having not undergone relaxation does not exhibit obvious refinement despite of its higher dislocation density. These results indicate that relaxation promotes bainite to refine, which is because deformed austenitic grains are divided by dislocation walls formed during relaxation and acicular ferrite formed before bainitic transformation.

关键词： stress relaxation strain induced precipitation refinement